Tubular cellulosic food casings are used extensively for processing a great variety of meat products and other food items. The food casings are generally thin-walled tubing of various diameters prepared from reconstituted materials, such as regenerated cellulose. Cellulosic food casings may also be prepared with fibrous webs embedded in the wall thereof, such casings commonly being referred to as "fibrous food casings."
The many different recipes and modes of processing that are used by the processed food industry to suit different tastes, and even regional preferences, generally necessitate the use of food casings with a variety of characteristics. In some instances, for example, food casings are required to have multifunctional uses wherein they serve as containers during the processing of a food product encased therein, and then also serve as a protective wrapping for the finished product. In the processed meat industry, however, the food casings used in the preparation of many types of meat products, such as various types of sausages, such as frankfurters, bolognas and the like, beef rolls, hams and the like, are frequently removed from about the processed meat product prior to slicing and/or final packaging.
Surface appearance and flavor are important factors in the commercial and consumer acceptance of processed meat products, and a common feature of most varieties of such products involves the use of "smoking" for imparting characteristic flavor and color thereto. The "smoking" of food products is generally accomplished by the food processor subjecting the food product to actual contact with smoke in a gaseous or cloud-like form. Such "smoking" processes, however, have not been considered completely satisfactory for a variety of reasons, including the inefficiencies and lack of uniformity of the "smoking" operation. Because of the shortcomings experienced, many meat packers now employ various types of liquid aqueous solutions of wood-derived smoke constituents, commonly called "liquid smoke solutions" that have been developed and used commercially in the food processing industry for the processing of many types of meat and other food products. For convenience in this specification, these commercially available "liquid smoke" solutions in their as-purchased state will be frequently referred to herein as "as-is" liquid smoke.
Examples of processes for preparing as-is liquid smoke are described in U.S. Pat. No. 3,106,473, issued Oct. 8, 1963 to Hollenbeck, and U.S. Pat. No. 3,873,741, issued Mar. 25, 1975 to Melcer et al. The processes for making liquid smoke can be generally described as comprising: (1) heating wood in an oxygen-controlled atmosphere to effect the thermal decomposition of wood and to generate smoke, and (2) contacting the smoke with an aqueous solution to condense and to recover the coloring and flavoring constituents of the smoke. The condensed as-is liquid smoke solutions generally also contain various tarry-substances, as well as organic acids such as acetic acid.
The application of "liquid smoke solutions" to meat products is generally carried out in a variety of ways, including spraying or dipping an encased food product during the processing thereof, or by incorporating the "liquid smoke solution" in the recipe itself. The actual operation of "smoking" by spraying or dipping is not completely satisfactory due to inability to treat the encased product uniformly, and incorporation of "liquid smoke solution" in the meat recipe does not always provide the desired surface appearance because of dilution of smoke ingredients. Incorporation in the recipe also reduces the stability of the meat emulsion, and will adversely affect taste if high concentrations are used. Application of liquid smoke to encased food products by the food processor, such as by spraying or dipping, also causes unwanted pollution and equipment corrosion problems for the food processor. In addition, encased sausages treated by application of the liquid smoke during commercial processing have been found to yield, after peeling the casing from the treated encased food product, sausages which are lacking in smoke color uniformity between individual sausages and batches of sausages. Even more undesirable is the lack of uniformity of coloration which often appears on the surface of the individual sausage, including light and dark streaks, light and dark blotches, and even uncolored spots which especially appear at the ends of sausages.
Several methods are known for coating either the interior or the exterior of a food casing with various liquid substances designed to meet particular processing requirements, as, for example, substances that affect the adhesion properties of the casing. Some of the coatings known in the art contain a liquid smoke as a constituent thereof.
Known methods for coating an as-is type liquid smoke solution internally in a casing have been found to be costly and also to limit the speed of a continuous high speed production line.
Known methods for coating the external surface of a casing, particularly a cellulosic gel-stock casing, with as-is type liquid smoke solutions, result in problems due to the tar content of these smoke solutions. That is, during the coating process, tarry deposits accumulate on the carrier rolls and the squeeze rolls of the treatment unit, which eventually forces shutdown of the treatment system.
One solution to the above-mentioned problems of imparting smoke color and flavor to a foodstuff is to use "tar-depleted" liquid smoke solutions to coat the interior or preferably the exterior surface of the casing. However, until recently, tar-depleted liquid smoke solutions were unavailable, and methods for making the same were unknown. As indicated above, it has been found that when a cellulosic food casing, made from a fibrous or non-fibrous gel stock, is treated with a highly acidic (pH of about 2.0 to 2.5) tar-containing, aqueous liquid smoke, tarry deposits accumulate on the carrier rolls and the squeeze rolls of the smoke treatment unit, causing the casing to stick to the rolls and eventually forcing shutdown of the unit. The acidity of the liquid smoke also may interfere with peelability of the casing by interfering with the action of the peeling aid used, such as, for example, carboxymethyl cellulose. Aqueous liquid smoke solutions are generally very acid, having a pH of 2.5 or less and a titratable acidity of at least 3 weight percent.
It was found that tar could be removed from the liquid smoke by neutralizing the as-is liquid smoke under controlled temperature conditions to precipitate the tar, and the use of this neutralized, tar-depleted liquid smoke to treat a gel stock casing would eliminate the problem of tarry deposits. This process is disclosed and claimed in U.S. patent application Ser. No. 417,172, filed Sept. 14, 1982 by M. D. Nicholson, now U.S. Pat. No. 4,431,032.
Contrary to the previous belief in the art, the tar-depleted liquid smoke still possesses significant smoke coloring capability. It has been generally believed that the tars in a liquid smoke mainly contribute to the coloring ability of the liquid smoke. However, it has recently been found that this is not the case, but that other constituents of the liquid smoke, believed to be mainly the carbonyls, have a more significant role in the coloring ability of the liquid smoke.
Another method, using a "solvent extraction" process may be employed to make tar-depleted liquid smoke. For example, such a process is disclosed and claimed in U.S. patent application Ser. No. 417,173, filed Sept. 14, 1982 by M. D. Nicholson, now U.S. Pat. No. 4,431,033. This process comprises (a) contacting a tar-containing aqueous smoke solution having an absorptive power of at least about 0.25 at a wave length of about 340 nm, with either a nonreactive or reactive organic liquid solvent which has a hydrogen bonding solubility parameter of at least about 2.7, and which is immiscible in the aqueous liquid smoke solution under conditions sufficient to form a tar-enriched solvent fraction and a tar-depleted liquid smoke fraction, and (b) separating the liquid smoke fraction to form a tar-depleted liquid smoke. Using such a solvent extraction method, it is possible to make tar-depleted liquid smoke solutions having a high capability to impart smoke color, odor, and flavor, without requiring neutralization of the tar-containing liquid smoke.
The tar-depleted liquid smoke made from the solvent extraction process, unless it is neutralized, is generally highly acidic, which may also interfere with the action of the peelability agents, such as certain water soluble cellulose ethers, which may be used on the casing. To alleviate this problem, the tar-depleted liquid smoke may be partially neutralized. However, since the coloration ability of the liquid smoke declines with increasing pH, the tar-depleted liquid smoke is only "partially neutralized" to a degree such that the peelability agent is not significantly affected and the coloration ability of the smoke is retained. The term "partially neutralized", as used herein, is intended to refer to liquid smoke compositions having a pH greater than about 3, preferably having a pH within the range of from about 3 to about 6.5, and even more preferably having a pH within the range of from about 3 to 5. By providing a partially neutralized, tar-depleted liquid smoke made from a solvent extraction process, the problems due to acidity are avoided to a large extent while a significant degree of the coloring ability of the original as-is liquid smoke is retained.
The above described liquid smoke compositions, whether as-is or tar-depleted, have been found suitable for use with fibrous cellulosic food casings. When used with nonfibrous casings, however, it has been found that these liquid smoke solutions, in their unconcentrated, as-manufactured form, impart a smoke color, odor and flavor to the foodstuff, but not in a quantity sufficient to be acceptable for all commercial applications. Because nonfibrous casings are thinner than fibrous casings, the liquid smoke cannot be in a practical manner "coated" on, applied to, or incorporated in the casing to an extent sufficient to always impart the desired smoke color, odor and flavor to a foodstuff. These compositions, therefore, cannot be universally used, being restricted mainly for use with fibrous casings.
In order to provide liquid smoke solutions having coloring ability sufficiently high to be usable on non-fibrous casings, tar-depleted liquid smoke solutions have been concentrated to form tar-depleted concentrated liquid smoke solutions, for example, as disclosed in U.S. patent application, Ser. No. 465,924, filed on Feb. 14, 1983 by M. D. Nicholson and J. H. Beckman, now U.S. Pat. No. 4,540,613. The tar-depleted, concentrated liquid smoke solutions have a higher coloring ability. Therefore, it is possible when using casings coated with tar-depleted, concentrated, liquid smoke solutions, to have sufficient coloring ability to color lighter foodstuffs, even when using a nonfibrous casing.
Tar-depleted, concentrated liquid smoke solutions can be made by a process which comprises providing an unneutralized, tar-depleted liquid smoke composition made from a solvent extraction process, and concentrating the unneutralized tar-depleted liquid smoke. The concentrated, tar-depleted liquid smoke product has surprising and advantageous physical properties, and it may be optionally neutralized to provide a partially neutralized, concentrated, tar-depleted liquid smoke composition.
The tar-depleted, concentrated liquid smoke solutions, described above, avoid the difficulties inherent when an as-is smoke is concentrated, wherein there is an increased concentration of undesirable chemical substances, for example tars, and certain other constituents which are desirable, for example phenols, which contribute to the flavoring ability, but cause an undesirably "strong" or "creosotic" flavor in high concentrations.
One problem in concentrating liquid smoke solutions is that when a neutralized liquid smoke is concentrated to a suitably high degree for coating on nonfibrous casings, there is a significant and undesirable increase in viscosity, rendering the resulting concentrated, liquid smoke unsuitable for commercial use. The increase in viscosity of neutralized, as-is and tar-depleted liquid smoke solutions which are concentrated is in large part due to the presence of acids, mostly acetic acid, in the liquid smoke. Upon neutralization of the acids in the liquid smoke, salts of neutralization of these acids are formed, and it is these salts that are the substances which mainly contribute to the high viscosity. In non-concentrated smoke solutions which are neutralized, the concentration of these salts is generally not high enough to cause a difficulty. However, when a neutralized smoke is concentrated, the concentration of these salts increases proportionally with the degree of concentration, resulting in an excessive concentration of these salts and, thus, an undesirably high viscosity.
It has now been found by Nicholson and Beckman as disclosed in the above-cited U.S. application Ser. No. 465,924, that when concentrating an unneutralized, tar-depleted, liquid smoke, the acid content is not proportionally increased with the degree of concentration of the liquid smoke. That is, as the unneutralized, tar-depleted smoke is concentrated, the acids causing the viscosity difficulties are apparently volatilized to a significant degree. Thus, it is possible to make concentrated liquid smoke solutions, while retaining a suitably low viscosity. The tar-depleted concentrated liquid smoke compositions of the above cited Ser. No. 465,924, because of their low total acid content, have a low viscosity when neutralized. Additionally, they are also tar-depleted, and thereby provide the processing advantages heretofore found only with the use of unconcentrated, tar-depleted liquid smoke solutions. They also have substantially increased smoke coloring and flavoring abilities over unconcentrated, tar-depleted liquid smoke solutions.
There is also an increase in the viscosity of concentrated as-is smoke solutions, which may be due in part to the presence of the high molecular weight polymeric tar constituents in the liquid smoke composition. The low amount of tars in the tar-depleted concentrated liquid smoke compositions also contribute to the low viscosity of both the unneutralized and partially neutralized forms.
The tar-depleted concentrated liquid smoke solutions have many advantages. However, heretofore they required additional processing of as-is liquid smoke. The extra processing includes the treatment to tar-deplete the as-is smoke and the processing to concentrate the resulting tar-depleted liquid smoke, when a concentrated liquid smoke is desired. This extra processing of the as-is liquid smoke to prepare the concentrated and unconcentrated, tar-depleted liquid smoke solutions requires expensive processing equipment and extra labor costs. It would be an advantage, therefore, to produce tar-depleted liquid smoke solutions, having the coloring ability of either concentrated or unconcentrated liquid smoke solutions, without extra process steps beyond the condensation of the smoke vapors to form a liquid smoke solution.
In U.S. Pat. No. 4,359,481, issued Nov. 16, 1982 to Smits et al., is disclosed a process for making a liquid smoke having reduced tar-content by fractional condensation, i.e. by cooling the smoke vapors in various stages. The liquid smoke product of the Smits et al. is produced for its flavoring ability, and is not shown to have a high coloring ability.
An object of the invention is, therefore to produce tar-depleted liquid smoke solutions without the extra processing of as-is liquid smoke.
Another object is to provide a method for preparing tar-depleted liquid smoke solutions, characterized by fewer process steps and less expensive equipment than heretofore possible.
Another object of the invention is to provide a method to produce, from the condensation of smoke-vapors, tar-depleted liquid smoke solutions having degrees of coloring ability, equivalent to unconcentrated liquid smoke solutions.
Another object of the invention is to provide a method to produce, from the condensation of smoke-vapors, tar-depleted liquid smoke solutions having degrees of coloring ability, equivalent to concentrated liquid smoke solutions.
Another object of the invention is to produce tar-depleted liquid smoke solutions having a high content of carbonyls.
Another object of the invention is to produce tar-depleted liquid smoke solutions having a high coloring ability.
Another object of the invention is to produce a concentrated tar-depleted liquid smoke with high coloring ability and low viscosity.
Other objects will become apparent in the description that follows.